The impact of alkali equivalent on the corrosion resistance of steel bars in alkali-activated slag/sea sand mortar

The use of alkali-activated cementitious materials (AACMs) and sea sand to prepare mortar can help reduce the high carbon dioxide emissions associated with ordinary Portland cement and alleviate the shortage of natural aggregates. However, the chloride ions present in sea sand can increase the risk of rebar corrosion. Compared with traditional cements, AACMs may offer superior chloride ion binding capacity. Alkali-activated slag/sea sand (AASS) mortars with varying alkali dosages were prepared in this study. First, the mechanical properties of the AASS mortars were tested. Subsequently, electrochemical methods, including chloride ion fixation and pH analysis, were used to evaluate the corrosion resistance of rebars. The results showed that an increase in alkali dosage enhanced both the pH and the chloride ion fixation capacity, improving the corrosion potential, reducing the corrosion current density and increasing the polarisation resistance. Electrochemical impedance spectroscopy tests indicated optimal corrosion resistance at a 6% alkali dosage, with the best rebar passivation at this level. Analysis of hydration products revealed how the increased alkali dosage boosted chloride ion fixation and rebar corrosion resistance. The results of this work provide a theoretical basis for the application of AASS mortar in construction.